1. Field of the Invention
The present invention relates to a mold for synthesizing powder, and, more particularly, to a mold for synthesizing ceramic powder suitable for use as a mold system which is subjected to spark plasma sintering, which comprises a cylindrical mold body into which a powder material used to synthesize ceramic powder is charged, and a pair of mold covers respectively disposed in contact with the top and the bottom of the mold body, thus basically suppressing the production of aggregates in synthesized powder due to pressing and also enabling the mold system to operate even with a small amount of power, so that the system is prevented from malfunctioning and the power consumption thereof when operating may be reduced.
2. Description of the Related Art
In order to synthesize ceramic powder, spark plasma sintering methods are known to be useful under conditions of temperature lower than conventional synthesis temperatures and maintenance time shorter than the conventional maintenance time, and thus thorough research into them is ongoing.
The configuration of a conventional system used in the spark plasma sintering process is one that combines a mold and electrodes. As shown in FIG. 1, the mold 100 includes a mold body 101 into which a power material A used to synthesize powder is charged, and electrodes 102, 103 formed at the top and the bottom of the mold body 101. These electrodes are disposed in contact with a press unit 107 that applies pressure to the powder material A, so that the powder material A is pressed by the press unit 107 and is also heated by power supplied to the electrodes 102, 103 and thus synthesized into the desired powder.
In the drawing, the downward arrow indicates the direction of electricity flow.
So that electricity efficiently flows between the press unit 107 and the powder material A, a high pressure of ones to tens of MPa should be applied to the powder material A. When pressure is applied at high temperature in this way, the synthesized powder may form a neck due to sintering effects generated in the synthesis process and thus may undesirably form a large amount of aggregates. For reference, the case where sintering is carried out using powder having many aggregates is very problematic because the sintering density may be remarkably decreased due to pores formed in the aggregates.
Also because a mold is typically manufactured to be thick so as to withstand pressure, the body thereof is heated by allowing a large amount of current to flow through the press unit 107 having a smaller cross-sectional area than that of the mold body. As such, however, such current is intensively applied to the press unit 107, and thereby high resistance occurs, undesirably easily heating the press unit 107. Thus, there may be many cases wherein the temperature of the press unit becomes excessively higher than the temperature of the mold body, the powder material or the synthesized powder. Accordingly, in the case of powder synthesized near the press unit, undesired reactions that have an adverse influence on the properties of powder, such as the excessive growth of particles and pyrolysis at high temperature, may take place.
As the electrodes which are in direct contact with the press unit at high temperature and the mold having a high thickness are also rapidly heated, like the press unit, the spark plasma sintering furnace may malfunction, making it difficult to perform a synthesis process at high temperature for a long period of time.